Unit 3 - Infection And Response

Question 1

How does bacteria make you feel sick?

Answer 1

By producing toxins that damage your cells and tissues. They are dealt with by your white blood cells producing antitoxins which neutralise them.

Question 2

How does a virus make you feel ill?

Answer 2

They invade your body cells and rapidly reproduce inside, causing the cell to burst open, releasing many more viral cells into your blood streams. They are dealt with by your lymphocytes producing antibodies which bind to antigens on the surface of the virus, destroying them.

Question 3

What is a virus?

Answer 3

Viruses are not cells. They are even smaller than bacterial cells, about 1/100th of the size, and have antigens on their surface which trigger an immune response.

Question 4

What is a protist?

Answer 4

Protists are eukaryotic organisms, however, most of them are single-celled. Some protists are parasites which live on or inside other organisms, causing them damage. They are often transferred by a vector - an organism which carries and transfers the disease between organisms, but doesn’t get the disease itself.

Question 5

What is a fungi?

Answer 5

Some fungi are single-celled, whilst others have a body made from hyphae (thread-like structures). These hyphae’s can grow and penetrate human skin and the surface of plants, causing diseases. The hyphae can also produce spores, which can spread to other plants and animals.

Question 6

How are pathogens spread?

Answer 6

1. Drinking or bathing in dirty water.
2. Breathing in water droplets in the air contaminated by coughing or sneezing.
3. Directly touching contaminated surfaces.

Question 7

What is measles?

Answer 7

A viral disease spread by droplets from an infected persons coughing or sneezing. It can lead to pneumonia (lung condition), inflammation of the brain, or even death. Symptoms include a red skin rash and a fever. It can be prevented by vaccination at a young age.

Question 8

What is HIV?

Answer 8

A virus spread by sexual contact, exchanging bodily fluids (e.g. blood), or sharing needles. It can weaken the immune system until it can’t cope with other infections or cancer, this is referred to as AIDS (late stage HIV). Symptoms include flu-like symptoms. It can be controlled by antiretroviral drugs which stops the virus replicating in our body cells.

Question 9

What is tobacco mosaic virus (TMV)?

Answer 9

A virus that infects many species of plants. It causes a mosaic pattern on the plants leaves, discolouring them. This means the plant can’t carry out photosynthesis as well, so its growth is stunted.

Question 10

What is rose black spot?

Answer 10

A fungus spread through water or the wind. It causes purple/black spots on the leaves of rose plants, eventually causing them to turn yellow and fall off. This means photosynthesis can’t be carried out as much so the plants growth is stunted. It can be treated by using fungicides or by removing any affected leaves and destroying them.

Question 11

What is malaria?

Answer 11

A protist spread by mosquitoes (a vector) feeding on infected animals and injecting it into another animals blood stream by feeding on it. It can lead to repeating episodes of fever and can even be fatal. It can be prevented or reduced by stopping the mosquitoes from breeding, using insecticides, and using/sleeping with mosquito nets.

Question 12

What is salmonella?

Answer 12

A bacteria spread by eating contaminated food. It causes food poisoning through toxins produced by the bacteria, which can lead to fever, stomach cramps, vomiting and diarrhoea. Most poultry is vaccinated against salmonella to control the spread of the disease.

Question 13

What is gonorrhoea?

Answer 13

A sexually transmitted disease (STD) caused by bacteria. It’s passed on by sexual contact. Symptoms include pain when urinating, or a thick yellow/green discharge from the penis or vagina. It used to be treated with penicillin (antibiotic), but has become resistant over time. It can be prevented by using barrier methods of contraception.

Question 14

How can the spread of disease be reduced?

Answer 14

Being hygienic, destroying vectors, isolating infected individuals, or vaccination.

Question 15

How does the skin help with fighting disease?

Answer 15

It acts as a physical barrier to pathogens. It also secretes anti-microbial oil from your pores which kills pathogens.

Question 16

How does your cardiovascular system help with fighting disease?

Answer 16

Cilia (hair-like structures) wafts up mucus produced by your bronchi into the throat, where it can be swallowed into the stomach. This mucus can be found in your nose and throat which traps pathogens until swallowed.

Question 17

What is phagocytosis?

Answer 17

The process by which white blood cells engulf foreign cells and digest them.

Question 18

What are antibodies?

Answer 18

Antibodies are proteins produced by your lymphocytes (white blood cells) when a foreign antigen is detected. Antibodies are specific to the pathogen and bind to antigens on their surface, destroying them.

Question 19

How do vaccinations work?

Answer 19

A dead or weakened version of the pathogen is injected into the patients blood stream. Even though the pathogen is harmless due to being dead/weakened, it still carries antigens which triggers an immune response. Lymphocytes produce antibodies specific to the pathogen, binding to its antigens and destroying it fairly easily. When the body is next exposed to the pathogen, memory cells can detect and recognise it, alerting the lymphocytes which can then rapidly mass-produce those specific antibodies to kill the pathogen. Vaccinations have played a massive role in eliminating a large number of common disease globally, however, the body may occasionally react negatively to the vaccine, potentially resulting in fever or seizures.

Question 20

What are antibiotics used for?

Answer 20

They kill or prevent the growth of bacterial cells without destroying your own body cells.

Question 21

How does bacteria become resistant to antibiotics?

Answer 21

1. Some bacteria can mutate and become resistant to antibiotics.
2. Others are able to become resistant by adapting to the antibiotics used. This can happen by overprescribing antibiotics for minor illness, allowing bacteria not targeted by the antibiotics to adapt. It can also happen by not finishing your full dosage, leaving some bacterial cells still alive to continue rapidly reproducing and releasing toxins.

Question 22

What are two plant-based drugs?

Answer 22

1. Aspirin is a painkiller used as a painkiller to lower fever. It was developed from a chemical found in willow tree bark.
2. Digitalis is used to treat heart conditions. It was developed from a chemical found in foxgloves.

Question 23

What was the first antibiotic drug discovered?

Answer 23

Penicillin was the first antibiotic. It was discovered by Alexander Fleming who was clearing out Petri dishes containing bacteria in his lab. The noticed that one of the Petri dishes had been contaminated with mould, but had also realised that the mould was creating clear rings around it killing any bacteria around it.

Question 24

What is efficacy and toxicity and when are they tested for?

Answer 24

Efficacy is whether the drug works and produces the effect that doctors are looking for. Toxicity is how harmful the drug is. They are all tested for on live animals (usually mammals) during the preclinical testing stage.

Question 25

How is dosage found?

Answer 25

After preclinical testing, the drug is given at an extremely low dosage to healthy, human volunteers in the clinical trial. The dosage is gradually increased over time to find its best efficacy before the toxicity becomes too harsh and makes the volunteers health worse.